Sherardia L.

Scientific Description

Common name. Madder. Family Rubiaceae.

Habit and leaf form. Herbs. Annual. Young stems tetragonal. Self supporting, or climbing; scrambling. Helophytic, or mesophytic, or xerophytic. Leaves whorled (or at least ostensibly so, seemingly representing paired leaves with enlarged, leaflike interpetiolar stipules); 4–6 per whorl; petiolate to sessile; connate (via the stipules), or not connate; gland-dotted, or not gland-dotted; simple; epulvinate. Leaf blades entire; one-veined, or pinnately veined; cross-venulate. Leaves with stipules. Stipules interpetiolar; with colleters (secreting mucilage), or without colleters. Leaf blade margins entire, or serrate. Leaves without a persistent basal meristem. Domatia recorded, or not recorded; represented by pits, or pockets, or hair tufts. Stem anatomy. Nodes unilacunar, or tri-lacunar. Secondary thickening developing from a conventional cambial ring.

Reproductive type, pollination. Fertile flowers hermaphrodite. Unisexual flowers absent. Plants hermaphrodite. Plants homostylous, or heterostylous. Entomophilous. Pollination mechanism conspicuously specialized (with passive pollen presentation involving stylar modification), or unspecialized.

Inflorescence and flower features. Flowers aggregated in ‘inflorescences’; in heads. The terminal inflorescence unit cymose. Inflorescences terminal (or rarely terminal on short axillary branches); a dichasium; with involucral bracts (the leaf-like bracts connate up to one-third of their length). Flowers small; regular; 4 merous (usually), or 6 merous; cyclic; tetracyclic. Free hypanthium present, or absent (depending on interpretation). Perianth with distinct calyx and corolla; 10; 2 -whorled; the two whorls anisomerous. Calyx 6; 1 -whorled; gamosepalous; lobed; open in bud; regular; persistent (3 persistent on each mericarp). Corolla 4; 1 -whorled; gamopetalous. Corolla lobes markedly shorter than the tube. Corolla imbricate, or valvate, or contorted; funnel-shaped; regular; pink to purple (in S. arvensis). Androecium 4. Androecial members adnate (filaments mostly fused to the corolla tube); free of one another; 1 -whorled. Androecium exclusively of fertile stamens. Stamens 4; isomerous with the perianth; oppositisepalous. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate; unappendaged. Pollen shed in aggregates, or shed as single grains; if aggregated, in tetrads. Gynoecium 2 carpelled. The pistil 2 celled. Carpels reduced in number relative to the perianth. Gynoecium syncarpous; synovarious to synstylovarious; inferior. Ovary plurilocular; 2 locular. Gynoecium transverse. Epigynous disk present. Gynoecium stylate. Styles 1; forked (2-lobed); attenuate from the ovary, or from a depression at the top of the ovary; apical; shorter than the ovary at anthesis to much longer than the ovary at anthesis. Stigmas 2; 1 - lobed; capitate; wet type, or dry type; papillate, or non-papillate; Group II type and Group IV type. Placentation axile. Ovules 1 per locule; pendulous, or horizontal, or ascending; anatropous, or hemianatropous.

Fruit and seed features. Fruit non-fleshy; indehiscent, or a schizocarp (? 2-lobed but usually not breaking freely into mericarps). Mericarps when present, 2. Fruit 2 seeded. Seeds endospermic, or non-endospermic. Endosperm ruminate, or not ruminate; if present, oily. Seeds winged, or wingless. Cotyledons 2. Embryo straight, or curved. Seedling. Germination phanerocotylar, or cryptocotylar.

Physiology, biochemistry. Aluminium accumulation demonstrated, or not found.

Geography, cytology, number of species. Adventive. Australian states and territories: Western Australia, South Australia, Northern Territory, New South Wales, Victoria, Australian Capital Territory, and Tasmania. South-West Botanical Province.

Etymology. After William Sherard, 1659–1728, English botanist and antiquarian who left a bequest to found a chair of botany at Oxford.